In general, a seal ring or the like employed in an electronic component storing package is known. In Japanese Patent Laying-Open No. 2006-49595, for example, there are disclosed a method for forming a silver solder clad material including a base material layer made of Fe—Ni—Co alloy and a silver-based brazing filler metal layer by firing or the like after applying a paste made of a mixture of silver-based brazing filler metal powder containing Ag, Cu, and Sn and media onto one surface of a base material made of a Fe—Ni—Co alloy plate, and thereafter forming a ring body (seal ring) by punching the silver solder clad material in a ring shape.
If a tiny protrusion (burr) is formed on a surface of the base material layer closer to the silver-based brazing filler metal layer to protrude toward the silver-based brazing filler metal layer when the silver solder clad material is punched in the ring shape, an interval between the surface of the base material layer closer to the silver-based brazing filler metal layer and a base is increased due to the tiny protrusion when the silver-based brazing filler metal layer of the ring body is melted to bond the base of an electronic component storing package and the ring body to each other. Consequently, a clearance is easily generated between the ring body and the base, and hence there is such a problem that the sufficient airtightness of the electronic component storing package is not retained in the case where the electronic component storing package is constituted by the ring body and the base. Therefore, the tiny protrusion is formed to protrude toward the base material layer when the silver solder clad material is punched in the ring shape.